Home › Weaving Calculations › Lecture 17
Weaving Calculations · Lecture 17
Blended Fabrics – Fibre Composition
Percentage of each fibre in a fabric whose warp and weft are different blends, and the elastane content of a core-spun yarn.
Fibre %Cotton / polyesterLycra core-spunDraft
Composition from yarn weights
The fabric label must state the fibre content by weight. Compute the warp and weft weight per yard exactly as in Lecture 5, then apportion each by its blend.
| A | B | C | |
|---|---|---|---|
| 1 | Warp | Weft | |
| 2 | Count Ne | ||
| 3 | Threads per inch | ||
| 4 | Width (in) | ||
| 5 | Contraction | ||
| 6 | Cotton share of this yarn | ||
| 7 | Weight per yard of fabric (lb) | 0.2475 | 0.2363 |
| 8 | Cotton (lb) | 0.2475 | 0.0827 |
| 9 | Polyester (lb) | 0.0000 | 0.1536 |
| 10 | Fabric composition | 68.3% | 31.7% |
blue = input (edit me)grey = formula (click to see it)
An all-cotton warp with a 65/35 polyester-cotton weft gives a fabric of about 83% cotton / 17% polyester — because the warp carries more than half the weight.
Lycra in a core-spun yarn
A core-spun stretch yarn wraps cotton around an elastane (Lycra) filament. The filament is fed under draft (stretched 3.9–4.2 times), so only 1/draft of its nominal denier ends up per unit length — then it relaxes a little (residual shrinkage) and grows again. The denier of the whole yarn is 5315 ÷ Ne.
| A | B | C | |||
|---|---|---|---|---|---|
| 1 | Yarn A | Yarn B | |||
| 2 | Yarn count Ne | ||||
| 3 | Lycra filament (denier) | ||||
| 4 | Draft on Lycra | ||||
| 5 | Residual shrinkage | ||||
| 6 | Denier of the yarn (5315 ÷ Ne) | 177.17 | 265.75 | ||
| 7 | Lycra denier in the yarn | 10.98 | 17.67 | ||
| 8 | Lycra % in yarn | 6.20% | 6.65% | ||
| 9 | Fabric: cotton warp (lb/yd) + core-spun weft (lb/yd) | ||||
| 10 | Warp weight per yard (100% cotton) | ||||
| 11 | Weft weight per yard (core-spun yarn B) | ||||
| 12 | Fabric Lycra % | 3.2% | |||
| 13 | Fabric cotton % | 96.8% | |||
blue = input (edit me)grey = formula (click to see it)
A 70-denier Lycra drafted 4.2× contributes 17.7 denier to an Ne 20 yarn — 6.65% of the yarn, and only about 3.2% of the fabric once the all-cotton warp is counted. Stretch fabrics are labelled “97% cotton 3% elastane” for exactly this reason.
Original lecture material
Open the file this page was built from: